This invention relates generally to the field of catheters. More specifically, this invention relates to catheters for establishing independent electrical contact between an electrical signal generating means and the surfaces of the atrium and ventricle of a heart.
As is recognized clearly by those skilled in these arts the rhythm of the beat of the heart is controlled naturally by a small mass of specialized muscle tissue in the heart known as the sino-atrial node (SA node).
In some cases of heart disorder or heart disease, however, the heart becomes unable to regulate its own pumping frequency. It is known that in such cases the frequency of heart pumping or heart beat may be artificially regulated by electrical stimulation. Thus electrical signal generating devices (pacemakers) are known which introduce an electrical pulse, for example a fine milliampere pulse, to the ventricle of the heart through a catheter.
Most known pacemakers in use are designed for ventricular pacing, i.e., to generate a signal which is carried through an implanted catheter conductor to the right ventricle of the heart thus providing direct stimulation only to the ventricle. This of course is not totally consistent with the normal pacing of the heart wherein the SA node operates to cause the atria to contract first, forcing blood into the ventricles which are then stimulated to contract and pump blood into the circulatory systems of the body.
In ventricular pacing, where the benefit of cooperative action between atrium and ventricle is absent, the inefficiency resulting from incomplete atrial filling of the ventricle may cause reduction in cardiac output by as much as twenty percent. Although such a reduction is acceptable in some patients it may well be critical in others and in such cases may result in heart failure or severe hypotension.
These problems attendant to ventricular pacing have not gone unrecognized. Various manufacturers have developed dual signal generating pacemakers which are designed either to pace the atria and ventricles in succession or to sense the patient's atrial contraction so as to pace the ventricle in response thereto a fraction of a second later.
The operation of such dual signal generating pacemakers requires an independent electrical connection between the pacemaker and the surfaces of the atrium and ventricle which are being stimulated or sensed. The presently practiced mode of establishing such electrical connection is to pass independent catheters through separate veins and into the atrium and ventricle to be served. Known atrial catheters have been unsatisfactory because of the inability to maintain a satisfactory electrical connection between the catheter conductor and the surface of the atrium which, unlike the surface of the ventricle, is smooth and unreceptive to the permanent lodging of a conductor tip.